1 in 2 El Ni簽o events could be extreme by mid-century
With the climate pattern known as El Ni簽o in full force from mid-2023 to mid-2024, global temperatures泭. As one of the strongest El Ni簽o events on record, it was likely the main culprit of unprecedented heat, floods and droughts worldwide.
In a published Sep. 25 in the journal Nature, a 51勛圖厙 climate scientist and collaborators reveal that the planet could see more frequent extreme El Ni簽o events by 2050 if greenhouse gas emissions continue to increase.泭
Its pretty scary that 2050 is not very far away, said Pedro DiNezio, the papers co-lead author and associate professor in the Department of Atmospheric and Oceanic Sciences. If these extreme events become more frequent, society may not have enough time to recover, rebuild and adapt before the next El Ni簽o strikes. The consequences would be devastating.泭
Pedro DiNezio
Shifting wind and soaring temperatures
El Ni簽o occurs when water temperatures along the equator in the Pacific Ocean rise by at least 0.9 簞F above average for an extended period.泭
The seemingly marginal temperature change can shift wind patterns and ocean currents, triggering unusual weather worldwide, including heat waves, floods and droughts.泭
When the area , scientists classify the El Ni簽o event as extreme. Since the U.S. National Oceanic and Atmospheric Administration began collecting data in the 1950s, the agency has recorded three to four extreme El Ni簽o events.泭
During an extreme El Ni簽o, the impacts on global weather tend to be more severe. For example, during the winter of 1997-98, 泭El Ni簽o brought , causing devastating landslides that killed more than a dozen people. Over the same period, the planet due to prolonged warming. 泭泭
Last winter El Ni簽o almost reached extreme magnitude, DiNezio said.泭
El Ni簽o events are difficult to simulate and predict because there are many mechanisms driving them. This has hindered our ability to produce accurate predictions and help society prepare and reduce the potential damage, they said.
Prior research suggests that climate change is intensifying and increasing the frequency of extreme weather events, possibly linked to changes in El Ni簽o patterns. However, due to limited data, scientists have yet to confirm whether El Ni簽o will strengthen with warming.
Satellite sea surface temperature departure in the Pacific Ocean for泭October 2015, where darker orange-red colors are above normal temperatures and are indicative of El Ni簽o.泭(Credit: NOAA)
DiNezio and their team set out to simulate El Ni簽o events in the past 21,000 yearssince the peak of Earths last Ice Ageusing a computer model.
The model shows that during the Ice Age, when Earths climate was colder, extreme El Ni簽o events were very rare. As the planet warmed since the end of the Ice Age, the frequency and intensity of El Ni簽o have been increasing.泭
The team validated the model by comparing the simulated data with past ocean temperature data retrieved from fossilized shells of foraminifera, a group of single-celled organisms ubiquitous in the oceans long before human existence. By analyzing the type of oxygen compounds preserved in these fossilized shells, the team reconstructed how El Ni簽o drove ocean temperature fluctuations across the Pacific Ocean for the past 21,000 years. The ancient record aligned with the models simulations.泭
We are the first to show a model that can realistically simulate past El Ni簽o events, enhancing our confidence in its future predictions. 泭We are also proud of the robust technique we developed to evaluate our model, but unfortunately, it brought us no good news, DiNezio added.泭
The model predicts that if society continues to pump greenhouse gases into the atmosphere at the current rate, one in two El Ni簽o events could be extreme by 2050.泭
The control knob
Despite El Ni簽os complexity, the model reveals that a single mechanism has controlled the frequency and intensity of all El Ni簽o events as the planet warmed since the last Ice Age.
When the eastern Pacific Ocean water warms from natural fluctuation, the winds that always blow east to west over the equatorial Pacific weaken due to changes in air pressure above the ocean. But during an El Ni簽o, weakened winds allow warm water to flow east, and the warmer water weakens the winds even more, creating a feedback loop known as the Bjerknes feedback.
DiNezios research suggests that as the atmosphere warms rapidly from greenhouse gas emissions, the planet experiences a stronger Bjerknes feedback, leading to more frequent extreme El Ni簽o events.
With the most recent El Ni簽o now in the past, DiNezio emphasized that society needs to focus on taking measures to reduce the impact of future extreme El Ni簽o events, including cutting emissions and helping communities, particularly those in the developing countries, become resilient to extreme weather.泭
We now understand how these extreme events happen, and we just need the will to reduce our reliance on fossil fuels, they said. Our findings emphasize the urgent need to limit warming to 1.5 簞C to avoid catastrophic climate impacts.泭
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